In a control system wherein a hydraulic servo valve is used to control the operation of a hydraulic motor, there will be a pair of hydraulic conduits or lines connecting the servo valve to the hydraulic motor. Sometimes it is necessary that these two hydraulic lines be connected to relief valve structure. The conventional manner of implementing this arrangement is to provide a separate relief valve in each line capable of venting the line to return fluid pressure. Where displacement of the associated hydraulic motor is quite limited, it is inevitable that the amount of fluid involved in the associated lines and the relief valve structure exerts a powerful effect on the effective spring rate of the system. Sometimes this change in spring rate may be sufficient to cause the system to oscillate. In addition to the problems introduced by adding the volume of operating fluid required for two separate relief valve structures and their associated springs and spring chambers, such an arrangement also requires greater space and weight and may result in some variations in threshold pressure from line to line should the individual springs vary somewhat in their rates.